In recent years, in order to address energy saving and global warming issues, renewable energy sources such as wind and sunlight have been attracting attention. Generally the capacity of such a renewable energy power generation system is small and in this case, the generation capacity is equivalent to the capacity of the transformer as a load connected with the system. Furthermore, as for conventional diesel generators and gas turbine generators, it is not uncommon that in a small scale system the generation capacity is equivalent to the capacity of the transformer as a load.
In such a system, if a circuit breaker or switch is turned on to magnetize the transformer, several kilo-amperes of inrush current flows due to saturation of the transformer core, which poses the problem that the output voltage of the generator declines. Also, when a plurality of transformers as loads are connected with the system, if during operation of one transformer another transformer is magnetized, the connected system might malfunction due to a decline in the supply voltage.
One solution to this problem is a closing resistor arrangement. In the closing resistor arrangement, two switches, a main and a sub switch, are used and the transformer is once magnetized through a resistor using the sub switch, then the resistor is bypassed using the main switch. In the closing resistor arrangement, the resistor suppresses magnetizing inrush current to solve the problem of a decline in the supply voltage.
Patent Literature 1 (JP-A No. 2002-75145) and Patent Literature 2 (JP-A No. 2006-155503) describe related techniques. Patent Literature 1 discloses a gas-blast circuit breaker in which a resistor for suppressing magnetizing inrush current is housed in a gas container and Patent Literature 2 discloses a closing resistor arrangement for the power supply system of a ship.